【作者】 张莹；

【导师】 郭安然；

【作者基本信息】 天津大学 ， 材料学， 2020， 硕士

【摘要】 莫来石纤维多孔陶瓷因其轻质、高孔隙率、抗热震性能优异、导热率低的特点而成为航空航天和能源工业领域中最常用的高温（>1300°C）隔热材料之一。然而,为适应日益增长的热防护需求,如何获得高强轻质的多孔陶瓷隔热材料是一个挑战。为解决这一问题,本论文借鉴广泛应用于热防护领域的微米纤维隔热瓦的设计思路,设计了一种以耐高温莫来石纳米纤维为三维多孔骨架的纳米纤维多孔陶瓷,并探究了不同工艺参数对莫来石纳米纤维多孔陶瓷性能的影响。获得具有均匀三维骨架结构的莫来石纤维多孔陶瓷是制备轻质高强隔热材料的关键。本文首先用静电纺丝制备的莫来石纳米纤维为原料,用琼脂糖凝胶注模的方法制备了不同琼脂糖含量的莫来石纳米纤维多孔陶瓷。不同琼脂糖含量能大幅影响样品密度,浆料中琼脂糖含量1.0wt%的样品具有最低密度为0.348 g/cm³,强度高达1.76 MPa,但由于样品收缩过大（46.35%）,样品密度大,热导率偏高(0.127 Wm^-1K^-1)。为了获得具有更低的导热系数的样品,我们采用叔丁醇基凝胶注模法制备了莫来石纳米纤维多孔陶瓷。随着纳米纤维的固相含量从1.5wt%增加到2.5wt%,样品从0.114 MPa增加到0.158 MPa。此外,探究了纤维长度对纳米纤维多孔陶瓷的影响,其结果表明与以短纤维为原料的样品相比,长纤维样品表现出更高的密度（0.062 g/cm³）低的导热系数(0.0597 Wm^-1K^-1)。通过比较发现密度为0.202 g/cm³的莫来石纳米纤维陶瓷的抗压强度（0.837MPa）明显高于莫来石微米纤维陶瓷（0.266 g/cm³）的强度（0.515 MPa）。本实验制备的莫来石纳米纤维多孔陶瓷是一种极具前景的高温隔热材料,适用于各种热防护系统。更多还原

【Abstract】 Mullite fibrous porous ceramics are one of the most commonly used high temperature（>1300°C）insulation materials in the fields of aerospace and energy industries owing to their low density,high porosity,excellent thermal shock resistance and low thermal conductivity.However,to keep up with the demand of the thermal protection,it is a challenge to improve the sample strength dramatically without sacrificing the low sample density.In order to solve this problem,we designed a nanofibrous porous ceramics with the three-dimensional porous skeleton formed by mullite nanofibers,based on the idea of the fabrication of the micron-fiber porous ceramics.And we investigated the effects of different preparation techniques and parameters on the properties of the mullite nanofibrous porous material.The key to the preparation of lightweight and high strength thermal insulation materials is to obtain mullite fibrous porous ceramics with uniform three-dimensional skeleton structure.In this paper,mullite nanofibrous porous ceramics with different agarose contents were prepared via agarose gel-casting using the electrospun ceramic nanofibers.The density of the materials could be effectively controlled by changing the content of agarose.The sample with 1.0wt%agarose content in the slurry has a minimum density of about 0.348 g/cm³ and a strength of 1.76 MPa.However,due to the excessive shrinkage（46.35%）,the density of the sample is too high,and the thermal conductivity is high(0.127 Wm^-1K^-1).To obtain low thermal conductivity samples,the mullite nanofiber porous ceramics were prepared by tert-butyl acrylamide gel-casting.The samples increased from 0.114 MPa to 0.158 MPa with the solid content of nanofibers increasing from 1.5wt%to 2.5wt%.In addition,the effect of fiber length on porous ceramics with nanofibers was investigated.Comparing with the samples using the short fibers,the samples using the long fibers as the raw materials show an ultralow density（0.062 g/cm³）and low thermal conductivity(0.0597 Wm^-1K^-1).The mullite nanofibrous ceramics with the density of 0.202 g/cm³ show a much higher compressive strength（0.837 MPa）than that of the mullite micron-fiber ceramics（0.515 MPa）with a little higher density（0.266 g/cm³）.The high-strength mullite nanofibrous porous ceramics is a promising high-temperature insulation material in various thermal protection systems.更多还原